There are several approaches available for bleaching and whitening teeth externally. Heat/catalyzed chemical procedures are well known. For example one technique involves vital bleaching of discolored or intrinsically stained teeth utilizing 37% phosphoric acid which etches the enamel, and then bleaching the teeth by applying 30% hydrogen peroxide to the tooth surface followed by heat application by a heating element. The time required will vary with tooth sensitivity. However, according to Bowles, et al., "Vital Bleaching: The Effects Of Heat And Hydrogen Peroxide On Pulpal Enzymes", Journal of Endodontics 12, 1084-112 (1986) both heat and hydrogen peroxide have been demonstrated to have deleterious effects on pulpal tissues.
Other techniques involve the superficial removal of enamel with abrasive instruments or pumice followed by treatment with additional caustic agents.
More recently, bleaching techniques suitable for home use have been developed. For example, Hayward, "Night Guard Vital Bleaching . . . ", Quintessence International 20, 173-177 (1989), describes a 10% carbamide (urea)/peroxide solution which is placed in a "Night Guard" and worn at night for several weeks to brighten teeth. According to Haywood, et al, no significant caustic chemical agents are used and only two short office visits are required to initiate treatment. This obviously provides a significant savings of cost and time for the patient.